In addition to an originating source node and a destination node, relaying generally involves a relay or relay node, and is therefore sometimes also referred to as relay-based communication. A classical wireless relay setup basically involves an originating source node (S) 50, a relay (R) 100, and a destination (D) 200, as schematically illustrated in FIG. 1.
In a first time phase, the originating source S transmits a message intended for the destination D, as illustrated in FIG. 1. This message transmission is also picked up by the intermediate relay R. In the next time phase, the relay R may re-transmit the received message to the destination D, as illustrated in FIG. 2.
Various relay communication schemes may be employed, e.g. a half-duplex Hybrid Amplify-and-Forward/Decode-and-Forward (hybrid AF/DF) relaying scheme may be used. In such an exemplary hybrid AF/DF protocol, the relay R detects whether it successfully receives a message from the source S, e.g. using a Cyclic Redundancy Checksum (CRC). If successful, the relay R re-encodes and transmits the message to the destination node D as in the DF protocol. If the transmission by the source S is not correctly decoded, the relay R amplifies and forwards the message as in the AF protocol [1]. The relay R is thus used as an intermediate node to assist the overall message transmission from source S to destination D.
As illustrated in FIG. 1, an interference source (I) may cause partial-time interference or partial-band interference during the first transmission. This may happen when the interference source I has a shorter transmission than the transmission from the source S, or when the interference source I acts as a “jammer” with partial-time or partial-band jamming. It is here assumed that the interference occurs in the first time phase.
Collaborative reception techniques for use in the presence of partial-time interference caused by partial-time jamming are proposed in reference [2]. Under the proposed techniques, a group of radios acts as a distributed antenna array by exchanging information that is then used to perform jamming mitigation.
An interference mitigation technique under partial-band interference caused by partial-band jamming (PBJ), called relay-based sub-band shifting method, is proposed in reference [3]. Through this approach, each sub-band of the amplified OFDM symbol at the relay can be changed by the predefined shifting rule of each relay, and the jamming effects at the destination may be partially removed.
A traditional way of R assisting the overall message transmission is that R decodes-and-forwards, or amplifies-and-forwards the information received from S. The disadvantage of this scheme is low spectral efficiency.
Another traditional way of R assisting the overall message transmission is that R waits for suitable feedback from the destination D and then sends what D needs. The disadvantage of this scheme is long delay.
The techniques proposed in [2] require a group of radios to act as a distributed antenna array by exchanging information that is then used to perform interference mitigation. The complexity is high. In addition, it is oriented to mitigate only partial-time interference.
The technique proposed in [3] also requires multiple terminals to share their resources to form a virtual antenna array, which increases the complexity.
Reference [4] relates to multi-user diversity scheduling in a wireless relaying network based on channel quality feedback from the receiving destination nodes.
Reference [5] relates to interference cancellation at the receiving end in a wireless relaying network.